The construct <link rel="stylesheet" href="main.min.css" /> doesn't raise the HtmlImportSettings.LoadFromUri event on import, as we currently require type="text\css" to be specified explicitly.
type attribute, but is actually now recommended practice.
Think of improving the message of the exception we throw if no data is loaded.
Workaround: set type explicitly:<link rel="stylesheet" type="text/css" href="main.min.css" />